Could be the valve train. It just seems loud in comparison to some other Fords, 5.0, 5.4, Ecoboost I've heard run. I don't have any other 6.2s to compare to so I may just be over thinking it.
It's made this noise since new, but I moved to Oklahoma City right after I bought it and its been so damn hot down here I've had the windows up for the last 3 months. I was pulling into the parking garage at work the other day with the windows down for the first time and it just seemed to make an excessive amount of noise under no load.
Truck runs great, other than the occasional bumble at idle, so I'm not overly concerned. I just figured I ask here first before I run around trying to get a dealer to look at it.